Full Idea
We need unities in order to be able to count: we should not therefore assume that such unities exist. We have borrowed the concept of unity from our concept of 'I' - our oldest article of faith.
Gist of Idea
Counting needs unities, but that doesn't mean they exist; we borrowed it from the concept of 'I'
Source
Friedrich Nietzsche (Writings from Late Notebooks [1887], 14[79])
Book Reference
Nietzsche,Friedrich: 'Writings from the Late Notebooks', ed/tr. Bittner,Rüdiger [CUP 2003], p.246
A Reaction
Personally I think that counting derives from patterns, and that all creatures can discern patterns in their environment, which means discriminating the parts of the pattern, which are therefore real and existing entities.